I can't comment on Cisco client to pix classic per say. But VPN across oceans depends a lot on what ISP is being used. If you use UUNET state-side and your client in Europe is on UUNET...you are likely to have a good environment for VPN. But some ISPs have poor peering arrangements making for poor throughput and long latencies across the pond. And then there are companies whose firewalls ban certain traffic. And there are companies that use PAT or Proxies. And then there are ISPs that use caching or proxying schemes. It comes down to setting expectations. Some folks expect the Internet to be no only essentially free - but to provide excellent performance to/from all locations all the time.
Sometimes you get what you pay for.
